When filling the fuel tank of a motor vehicle, a fuel pump arranged inside a fuel dispenser generates a stream of fuel from a fuel storage tank to the fuel tank of the vehicle. The fuel pump which must be able to pump liquid, flammable fuel, is a main component of the fuel dispenser. It is relatively expensive and requires a lot of room inside the fuel dispenser.
Moreover, it is a common measure to recover the vapor escaping the tank when filling it with the liquid fuel. This measure is taken for both safety and environmental reasons, since the fuel vapors are flammable and constitute a health hazard. The vapor recovery is achieved, for instance, by arranging a vapor suction nozzle next to a fuel dispensing nozzle of a pistol grip that is used for filling the tank with fuel. Vapor is then removed from the tank during filling, at a certain rate, which is often controlled by the standard rate. Vapor recovery systems typically comprise a pump for removing fuel vapor, from the tank of the vehicle, by suction and feeding it back to the fuel container from which the fuel is fed to the vehicle. This mutual exchange of vapor/fuel is continuously performed when filling a vehicle with fuel. Accordingly, at least two pumps are arranged in the fuel dispenser, i.e. the fuel pump for transporting the liquid fuel and the vapor recovery pump for transporting the gaseous fuel vapor.
A problem associated with prior art, in respect of both fuel pumps and vapor recovery pumps, is relatively high production costs due to complex arrangements. Maintenance is cumbersome and many of the techniques are sensitive to leakage of fluid past the piston. Another problem is that some of the arrangements are rather bulky and takes a lot of space when mounted inside a fuel dispensing unit.